What is the ruling on the loan my father took from the state to buy a car without interest, and then he was forced to take an interest-bearing loan from the bank to cover the additional costs of the same car, and is it permissible for me to use this car for my personal needs, and must I obey him if he orders me to use it for his needs?

It is not permissible to borrow with interest except in a dire necessity that would lead to destruction or something close to it, and buying a car does not fall under this category. The father must repent from this, and if it is possible to return the borrowed money without interest, then that is obligatory. Otherwise, it should be paid with the burden of the interest falling upon the lenders. He is not obliged to sell the car to repay the debt in one lump sum, because money acquired through a void contract must be returned to its owner. If he permits its delay, then he is not obliged to return it immediately. It is permissible for you to use the car purchased with money mixed from a permissible loan and an interest-based loan, because it contains permissible elements, and because money is not specifically designated according to the majority of scholars. And you must obey your father in fulfilling his needs with this car.